Vehicles may use electronic throttle control (ETC) to adjust a throttle position in an internal combustion engine. Further, a desired throttle position may be determined by various sensors such as an accelerator pedal position sensor, an engine speed sensor, a vehicle speed sensor, etc. Once the desired throttle position is calculated, an electric motor within the ETC is driven to the desired throttle position. Further, ETC is integrated with other electronic features such as cruise control, traction control, stability control, and other controls that contribute to torque management. Due to this electronic control over the throttle position, the throttle can move regardless of a position of an accelerator pedal, which can be problematic if the ETC is unpowered. Therefore, ETC is often integrated with an ability to assume a default position such that at least some intake air can reach the engine to avoid stalling.
For example, U.S. Pat. No. 6,155,533 describes an electronic throttle control system that includes a fail-safe mechanism. The fail-safe mechanism positions a throttle valve in a default position in the event of degradation of the electronic throttle control system. In one example, the throttle valve has a default (unpowered) position of seven degrees from a closed position to provide intake air to the engine.
The inventors herein have recognized various issues with the above system. For example, the fail-safe mechanism required to position the throttle valve at a precise default position that is not a closed position adds significant cost to the electronic throttle control system.
Accordingly, in one example, some of the above issues may be at least partly addressed by an engine including a first throttle valve. The first throttle valve is provided in a first intake passage coupled to an intake manifold. The first throttle valve has a default closed position. The engine further includes a second throttle valve. The second throttle valve is provided in a second intake passage coupled to the intake manifold. The second throttle valve has a default open position. The engine further includes a venturi pump that is provided between the second throttle valve and the intake manifold. When the second throttle valve is in the default open position, intake air flows through the venturi pump.
The default open position of the second throttle provides intake air to the engine so that the first throttle valve may be designed with a default closed position. In other words, the default open position of the second throttle valve provides similar functionality of the fail-safe mechanism with regard to providing intake air to the engine. Thus, by providing the second throttle valve with the default open position, the mechanism to hold the first throttle valve at a precise default open position may be eliminated, while maintaining similar functionality. In this way, the production cost of the engine may be reduced.
In some embodiments, the second throttle valve may be configured to provide air flow through the venturi pump to supply vacuum to a vacuum consumption device. The second throttle valve in combination with the venturi pump may replace the functionality of an electrically-driven vacuum pump (or engine driven vacuum pump) that would otherwise be used to provide vacuum to a vacuum consumption device. As such, an electrically-driven vacuum pump may be eliminated from the engine. In this way, the production cost of the engine may be further reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.